1. Field of the Invention
The present invention relates to an imaging apparatus such as a digital still camera or a digital video camera, and in particular, relates to an imaging apparatus enabling image capture with a reduced shutter time lag.
2. Description of the Related Art
In recent years, advances have been made with respect to higher pixel formation in image sensors used in imaging apparatuses such as digital still cameras or digital video cameras. Furthermore active research is being conducted into XY address sensors, as exemplified by complementary metal-oxide semiconductor (CMOS) sensors, provided with an amplification unit for each pixel.
Sensors provided with an amplification unit for each pixel may entail issues such as the production of noise caused by a characteristic variation in the pixel amplification unit, which may be mixed into the read-out pixel signal.
Japanese Patent Application Laid-Open No. 01-154678 discusses a sensor which eliminates this type of noise by subtracting a pixel signal output when an input to the amplification unit is reset, from the pixel signal.
For example, when reading a signal from a single horizontal pixel row, firstly the input of the pixel amplification unit for the single horizontal pixel row is reset and the resulting signal for the single horizontal row is stored as a noise signal.
Next, a single horizontal row pixel signal is read and the signal for the single horizontal row is stored separately from the noise signal. The sensor forms and outputs a group signal constituted by a pixel signal and a noise signal for each pixel. Consequently, a noise-reduced image can be produced by subtracting the noise signal from the pixel signal.
However, in Japanese Patent Application Laid-Open No. 01-154678, the time for reading operations is increased due to the necessity to read both the noise signal and the pixel signal. Consequently, when recording a still image, there may be an increase in the shutter time lag from the command for image capture to initiation of exposure for the captured image.